There’s a science to being happy, and it’s not as complicated as we sometimes think. According to research from happiness expert Sonja Lyubomirsky, only about 10 percent of our happiness comes from external circumstances (where we live, how much money we earn, etc.). We get another 50 percent of our happiness from our genes. And 40 percent is within our control. It comes directly from the choices we make.

Science now tells us that the lifestyle portion of our happiness is the only part that’s within our control, and we can optimize it by making tiny changes in how we live. Here are 15 scientifically proven suggestions for where to start.